Infections are known to spread through microorganisms such as bacteria, fungi, viruses, protozoa. Such microorganism can exist in room environments in the air or on exposed surfaces. When a person comes into contact with the pathogens they are at risk of developing an infection.
Hospitals are a particular concern. Nosocomial infections are common, costly and can be lethal. While good personal hygiene such as thorough hand washing among patients, physicians, nursing staff and other hospital staff can be a very effective tool to reduce contagion, the hospital environment itself can contribute to nosocomial infections by harboring virulent strains of bacteria, fungi and viruses that can cause infections. Surface decontamination is a critically important task to prevent nosocomial infections and techniques for decontaminating vary from washing surfaces with decontaminating chemicals to fumigation with gas. Fumigation is problematic because it is time consuming and requires the use of dangerous chemicals and evacuation of the used area for a considerable amount of time. Consequently it generally cannot be performed often enough to maintain a healthy level of topical decontamination in most environments. Topical antiseptics are often used for cleaning surfaces, but this too is a time consuming task, usually involving a human cleaner, which cannot be performed often. Moreover, not all surfaces can be easily cleaned and even on those that can be, this form of decontamination is subject to human error and its effectiveness cannot easily be quantified.
Ultraviolet (UV) germicidal radiation has been successfully used in purification and sterilization systems for various media, such as air, water, and food. Ultraviolet germicidal radiation has proven effective at destroying antibiotic resistant organisms. UV radiation is a particularly useful tool in the fight against hospital acquired infections superbugs such as Clostridium Difficile (C. Diff), Methicillin Resistant Staphylococcus Aureus (MRSA), Vancomycin Resistant Enterococcus (VRE), etc.
UV decontamination systems may sterilizes the media or surface by exposing it to ultraviolet radiation of a sufficient power and for a sufficient exposure time to destroy by dimerization of thymine pairs the DNA molecular structure of bacteria, viruses, protozoa, and other organisms, which may be present in the media.
U.S. Pat. No. 5,891,399 describes a UV air purification system that comprises UV light sources in a housing which has a fan to draw air through the housing to be exposed to UV radiation. When the room the housing is in is empty, covers can open to expose some surfaces of the room to the UV radiation. An IR detector can be used to cut off possible current supply to the UV lamps when a human being or animal enters the room in question.
U.S. Pat. No. 8,097,861 describes an elevator sanitizing system which has a UV light which can be rotated in to take the place of a visible light to sanitize the elevator inner surfaces. The system features a sensor for sensing the presence of a human and a sensor for sensing the when the elevator's doors are closed.